feat: add noir-compiler checks to aztec_macros (#4031)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

This PR moves the checks applied in
[noir_compiler](https://github.com/AztecProtocol/aztec-packages/blob/c38dbd2fe13dfcf019da3877c17ca8d148f45233/yarn-project/noir-compiler/src/contract-interface-gen/abi.ts#L92-L97)
to `aztec_macros`.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

aztec_macros/src/lib.rs

@@ -31,10 +31,15 @@ impl MacroProcessor for AztecMacro {
     }
 }
 
+const FUNCTION_TREE_HEIGHT: u32 = 5;
+const MAX_CONTRACT_FUNCTIONS: usize = 2_usize.pow(FUNCTION_TREE_HEIGHT);
+
 #[derive(Debug, Clone)]
 pub enum AztecMacroError {
     AztecNotFound,
     AztecComputeNoteHashAndNullifierNotFound { span: Span },
+    AztecContractHasTooManyFunctions { span: Span },
+    AztecContractConstructorMissing { span: Span },
 }
 
 impl From<AztecMacroError> for MacroError {
@@ -50,6 +55,16 @@ impl From<AztecMacroError> for MacroError {
                 secondary_message: None,
                 span: Some(span),
             },
+            AztecMacroError::AztecContractHasTooManyFunctions { span } => MacroError {
+                primary_message: format!("Contract can only have a maximum of {} functions", MAX_CONTRACT_FUNCTIONS),
+                secondary_message: None,
+                span: Some(span),
+            },
+            AztecMacroError::AztecContractConstructorMissing { span } => MacroError {
+                primary_message: "Contract must have a constructor function".to_owned(),
+                secondary_message: None,
+                span: Some(span),
+            },
         }
     }
 }
@@ -340,6 +355,28 @@ fn transform_module(
             has_transformed_module = true;
         }
     }
+
+    if has_transformed_module {
+        // We only want to run these checks if the macro processor has found the module to be an Aztec contract.
+
+        if module.functions.len() > MAX_CONTRACT_FUNCTIONS {
+            let crate_graph = &context.crate_graph[crate_id];
+            return Err((
+                AztecMacroError::AztecContractHasTooManyFunctions { span: Span::default() }.into(),
+                crate_graph.root_file_id,
+            ));
+        }
+
+        let constructor_defined = module.functions.iter().any(|func| func.name() == "constructor");
+        if !constructor_defined {
+            let crate_graph = &context.crate_graph[crate_id];
+            return Err((
+                AztecMacroError::AztecContractConstructorMissing { span: Span::default() }.into(),
+                crate_graph.root_file_id,
+            ));
+        }
+    }
+
     Ok(has_transformed_module)
 }